In the past, attempts have been made to reduce the unwanted microphonic signal in pyroelectric detectors by mechanical design, electrical design, or both. A mechanical design places the electret on a platform optimized for dampening microphonic resonances. A platform, however, is not optimum because an electret of nonuniform thickness and/or heat sink conditions will not be spatially uniform. The simplest electrical design uses two identical electrets with the anode of one connected in parallel with the cathode of the other. Multiple electrode schemes have been used on a single electret to reject microphonic signals. Domain engineering techniques have also been used. Domain engineering techniques in materials such as LiNbO.sub.3 have required the use of an ion mill. This resulted in very small fragile detectors. Domain engineering in polymers such as polyvinyladine flouride has also been used, but such detectors do not have the same pyroelectric coefficient as those made from LiNbO.sub.3 and LiTaO.sub.3. They also result in detectors that do not have a highly uniform thickness.
Representative of the art is:
U.S. Pat. No. 4,967,082 (1990) to Cooke et al. discloses a thermal radiation detection apparatus comprising an array of pyroelectric detectors 1, 2, 3, 4 in which compensation is provided for the effect of ambient temperature changes on the detector outputs and also for dc offsets which occur in source follower impedance converters 13 that are necessarily used with each detector.
U.S. Pat. No. 4,963,741 (1990) to McMullin discloses a large area pyroelectric joulemeter for measuring the pulsed beam output of a laser.
U.S. Pat. No. 4,943,800 (1990) to Ikeda et al. discloses the method of mounting three pyroelectric detectors to eliminate microphonic noises caused by temperature variations.
U.S. Pat. No. 4,920,385 (1990) to Clarke et al. discloses electro-optical sensing of form type and other defects on surfaces such as sheet metal or plastic panels.
U.S. Pat. No. 4,792,682 (1988) to Endou et al. discloses a pyroelectric infrared temperature compensated detector. The system utilizes one operating area of the pyroelectric detector as an infrared detection area. Similar to the concept as disclosed in Fisher below, the compensation signal is obtained from other operating areas of the pyroelectric detector. Microphonic noises caused by vibration and temperature variations are reduced.
U.S. Pat. No. 4,629,319 (1986) to Clarke et al. discloses electro-optical sensing of form type and other defects on surfaces such as sheet metal or plastic panels.
U.S. Pat. No. 4,598,163 (1986) to Ito discloses a pyroelectric detector comprising a functional portion in which opposed electrodes 111 to 118 are formed on both surfaces of a pyroelectric-type substrate 101, and four light-receiving electrode portions a, b, c, and d are structured by the opposed electrodes 111 to 118. The light-receiving electrode portions a and c and the light-receiving electrode portions b and d are electrically connected alternately and in series, and the light-receiving electrode group A and the other light-receiving electrode group B are connected to have opposite polarities.
U.S. Pat. No. 4,593,456 (1986) to Cheung discloses a thermal detector array which includes a substrate layer with a pyroelectric layer attached to the substrate, a plurality of detector regions being defined in the pyroelectric layer by openings through the layer.
U.S. Pat. No. 4,542,294 (1985) to Tamura et al. discloses a method of producing a pyroelectric-type infrared detector comprising the steps of arranging two pyroelectric elements 25A and 35A polarized in opposite directions on support blocks 21A, and arranging, in combination, the support blocks 21A on which the pyroelectric elements 25A and 35A are arranged on a common base plate 40.
U.S. Pat. No. 4,532,424 (1985) to Cheung discloses a thermal detector array which includes a substrate layer with a pyroelectric layer attached to the substrate, a plurality of detector regions being defined in the pyroelectric layer by openings through the layer.
U.S. Pat. No. 4,441,023 (1984) to Doctor et al. discloses a dual pyroelectric crystal sensor suitable for infrared intruder alarms and the like having two separate closely-spaced identical pyroelectric crystal detectors connected in parallel opposition.
U.S. Pat. No. 4,224,521 (1980) to Fisher discloses in FIG. 1 a detector array and a circuit which sum the output of each detector with an average output signal obtained from all detectors. This technique serves to cancel microphonic noise caused by vibration and temperature variations.
U.S. Pat. No. 4,110,616 (1978) to Porter et al. discloses a pyroelectric detector which includes at least one pyorelectric element consisting of a pyroelectric material sandwiched between first and second electrodes and a semiconductor chip having a field effect transistor formed on one surface and having an electrical contact for the gate electrode of the transistor formed on the surface opposite to one surface.
U.S. Pat. No. 4,060,729 (1977) to Byers et al. discloses the concept of mounting two pyroelectric detector elements in adjacent configuration. Different or the same polarization of the elements are used to cancel noise signal created by temperature variations and vibration.
U.S. Pat. No. 3,453,432 (1966) to McHenry discloses the concept of placing an active pyroelectric detector adjacent to a compensating pyroelectric element to cancel undesirable signals generated due to substrate temperature changes.
What is also needed is a pyroelectric detector having adjacent domain reversed regions. What is needed is a pyroelectric detector having domain engineered regions to eliminate microphonic noise and/or enable position sensing. What is needed is a pyroelectric detector having a thick electret to simplify the manufacturing and augment the use of the detector by reducing the mechanical frailty present in the prior art detectors and eliminate the need for ion milling procedures. What is needed is a pyroelectric detector having an electrically conducting container and contiguous ground electrode which electrically isolates the signal electrode from electromagnetic interference. What is needed is a pyroelectric detector having a large detector area.